Alerting the public in case of an emergency event is legally mandated in many countries. Examples for emergency events are environmental disasters like earthquakes or thunderstorms or volcano eruptions, industrial catastrophes like nuclear or chemical plant explosions, or terrorist attacks or wars.
Traditionally, the public is informed on emergency events via FM-radio or television (TV). Accordingly, emergency information comprising e.g. information about the emergency event and security instructions is broadcasted via FM- or TV channels to radio or TV devices, respectively. However, those devices are typically stationary devices like a home TV or a home hifi-unit or quasi-stationary like a car radio, i.e. a drawback of such traditional emergency alert systems is that mobile users that typically do not carry such stationary or quasi-stationary devices can not be alerted immediately in emergency events.
Recently, in November 2001, a cell broadcast system was described by CMG Wireless Data Solutions, 2001 (Internet Publication© November 2001) to alert citizens via cell broadcast in case of an emergency event. The system basically consists of a call center and a mobile communication network. The call center can be called for informing the call center about an emergency event, e.g. via 112 emergency call, optionally supplemented with location information derived from the location of the calling mobile terminal to indicate to the call center the location of the emergency event. Based on that information, the call center can select a geographical area and can send short message service messages (SMSs) via cell broadcast to mobile phones in that particular geographical area to inform the corresponding users about the event.
SMS, however, is restricted to short text messages with max 160 characters. Such short text may be sufficient for an immediate warning about an emergency event, however the content and scope of information is very limited and the adaptation of often complex emergency information to such a short text message may cause time delays and misinterpretation at the sending and receiving end, both harmful in emergency situations.
Furthermore, the CMG system is susceptible to network congestion, i.e. emergency SMSs may not be delivered or may be delayed in case the mobile network is congested. Especially in emergency situations wherein people tend to call official agencies or relatives on a large scale, network congestion can be very problematic.
Moreover, on each mobile phone a cell broadcast reception setting has to be active to receive messages via cell broadcast service (CBS). However, users are often not aware of this feature and do not manually activate it or tend to manually deactivate this feature such that a large fraction of the mobile phones in a cell thus do not receive cell broadcast messages which makes current cell broadcast systems insecure for informing of an emergency event.